Depletion of functionally active CD20+ T cells by rituximab treatment

Abstract

Objective. Rituximab is a therapeutic anti-CD20 antibody used for in vivo depletion of B cells in proliferative and autoimmune diseases. However, the mechanisms of action are not fully understood, since not all of the therapy-mediated effects can be explained by the depletion of antibody-secreting cells. In addition to B cells, there is also a small population of T cells coexpressing CD20 in all individuals. This study was conducted to examine the phenotype and function of CD3؉CD20؉ T cells in patients with rheumatoid arthritis (RA) and healthy controls.Methods. The phenotype and apoptosis of peripheral blood mononuclear cells from healthy donors and RA patients were examined by 4-color fluorescenceactivated cell sorting analyses. Cytokine production was determined by intracellular staining and measurement of cytokines in the supernatants. Proliferation of sorted T cell populations was analyzed using 3 H-thymidine uptake assays.Results. In healthy individuals, 0.1-6.8% of peripheral blood T cells (mean 1.6%; n ‫؍‬ 142) coexpressed CD20, which was not significantly different from that in the peripheral blood of RA patients, in whom 0.4-2.6% of T cells (mean 1.2%; n ‫؍‬ 27) were CD20؉. During rituximab therapy, the CD20؉ T cells along with the B cells were eliminated from the RA peripheral blood. Among the CD20؉ T cells, 45% coexpressed CD8 and 55% coexpressed CD4. Polyclonal CD3؉CD20؉ cells were functionally characterized by constitutive cytokine production (i.e., interleukin-1␤ and tumor necrosis factor ␣), a low proliferative capacity, a high activation state, and enhanced susceptibility to apoptosis.Conclusion. These findings suggest that CD20؉ T cells represent a terminally differentiated cell type with immune-regulatory and proinflammatory capacities. Depletion of CD20؉ T cells may be an additional mechanism by which anti-CD20 therapy functions in patients with RA.

CD3+CD20+ cells may be an artifact of flow cytometry: Comment on the article by Wilk et al

“…We first characterized the phenotype of these T cells in peripheral blood mononuclear cells (PBMCs) from 28 normal donors (mean Ϯ SEM age 44.6 Ϯ 8.3 years [range 28-58]) and found, consistent with the reports by Wilk et al (1) and others (2,7,8), that CD3ϩCD20ϩ cells were present in the peripheral blood of normal donors, at frequencies ranging from 0.11% to 5.7% in our study (mean Ϯ SEM 2.2% Ϯ 0.4%), with no correlation with donor age. Using samples from 10 normal donors, we compared the marker frequencies of such…”

“…Wilk et al recently reported findings suggesting that rituximab treatment in rheumatoid arthritis is associated with depletion of a small T cell subset expressing the CD20 B cell marker (1). Expression of the CD20 molecule by leukemic T cells has been demonstrated by immunohistochemistry (2-6), raising the question of whether these leukemic cells resulted from abnormal expression occurring during the malignant transformation process, or whether they resulted from the transformation of a small CD20ϩ T cell subset existing at a normal state.…”

Complement factor H-derived short consensus repeat 18-20 enhanced complement-dependent cytotoxicity of ofatumumab on chronic lymphocytic leukemia cells

“…The non-significant drop in T-cell counts may be due to the recently reported expression of CD20 in a small subpopulation of the CD3 + T-cell pool. 34 The previously reported increased lysis of erythrocytes in the presence of the C terminal fH domain was observed when the classical pathway was blocked by Mg-EGTA, suggesting the involvement of the alternative complement pathway. 31 In our approach it is most likely that the initial complement activation occurs via the classical pathway, as in the absence of ofatumumab no cell lysis and no presence of the active C3 α' chain was observed.…”

Immunological changes in diffuse large B-cell lymphomas after Rituximab-CHOP treatment: Own data and review of the literature

“…A T-sejtek kb. 6%-án kimutatható CD20 expresszió [10], és a memóra típusú CD4 + Tsejtek kialakulásában, érésében a B-sejtek antigén prezentálásának is valószínű a szerepe [11].…”